In the process of building a Ranger myself and decided to verify fin sizes. The patterns printed directly from JimZ's site, with no scaling (as is) DO NOT match the current Bertha fins nor the Ranger fin pattern given in the plan set distributed thru the NARTREK packages. For reference, the NARTREK pattern matches the Bertha fins and the NARTREK pattern does appear to have been re-printed from the original plans.

I agree that internet info should not be blindly trusted, but it seems that if a scaling process is used, it should be noted, otherwise the plans are pretty much useless at that point.

As a professional involved day to day with construction plans, I would never think of releasing a plan sheet without a precise scale shown OR actual dimensions listed. Any other opinions?

And that's why you'll see an attempt to add a scale to fin/decal scans on this web site.

When you are getting fin patterns scans or decal scans from YORP or JimZ, you need to be sure that you print the scans at the same dpi (image resolution) that they were scanned at. The plans at JimZ's site are scanned at 300dpi, and I believe that the plans at YORP are also at 300dpi, except where noted (e.g., Estes World Federation Star Probe at 150dpi). You can use a graphics program like the free, open source program The GIMP (Windows, Mac, Unix/Linux versions) to adjust an image's resolution (i.e., rescan the image) to the correct resolution.

If you need help in making this correction using The GIMP, let me know and I will outline the steps to take (the process is actually quite simple).

Mark \\.

Sorry for being late to this party...

The original EIRP design, #13, for the Big Bertha, does show BFS-30 sheet stock for the fins, which is 3/32" thick. The oldest kit plan scan that I have shows this was changed to BFS-40, or 1/8" thick. This plan has the line drawing of the Big Bertha in RED ink at the top of the page, so whenever this printing of the plan was released, that's an indicator of the change date.

Comparing the K-6 Ranger fin outline to the K-23 Big Bertha outline, there is a slight difference. The Ranger fin is 1/4" shorter. The outlines are the same in all respects, until you get to the trailing edge. It looks like Estes added 1/4" to the bottom when the Big Bertha was created. This may have carried over to later production of the Ranger, however the sheet that I'm looking at shows BFS-30 as the fin stock.

The EIRP #13 sheet shows the longer fin, BTW.

I just printed out three sets of fin patterns, using Photoshop Elements 5 - one of the EIRP #13 sheet, one from JimZ K-23 Big Bertha file set, and one from the K-6 Ranger set. All three patterns match each other on outline and overall size, with the exception of the Ranger which is 1/4" shorter than the Big Bertha.

I also have a 25-plus-year-old Big Bertha kit, and I compared my printouts with those fins. The root edge length is 3 3/4" on the kit. The three scans, respectively, show 3 13/16" for the EIRP #13 Big Bertha, 3 5/8" for the K-6 Ranger, and 3 13/16" for the K-23 Big Bertha.

Some of these differences can be attributed to the scanners used to digitize them, and to any "cleaning up" that might have been done to the image. Even the original line art might not be exactly the same as what the plan shows - slight image stretching or shrinkage may have occurred when those images were printed. Paper shrinkage or swelling could account for the 1/16" discrepancy, as could the sanding of the fins when the kit was built.

My Ranger's paint job is based on the one in an early-60s catalog:





The catalog photo was B&W, so I just guessed that it was red. I've since added a black stripe amidships.

Wow :eek:

That ranger is as big as a tree :eek: :eek: :eek:

Yes, basically it all falls into the "acceptable range of variation".

I've had many folks tell me I have a great looking (insert rocket name here). No one has ever said that "the root edge looks to be 1/16 of an inch short." :D

Frankly, about the only time really tight tolerances are needed with fins is when pieces need to fit together. The caps on the Sprite fins come to mind. The conformal fins on the Beta are another good example. Even then, FNF is really good for correcting "dimensional inexactness" :D

Doug


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Well, you're lucky then. :cool:

I first had my Nike Hercules on display as Peter Alway walked by he says, "Fins are too small." and just keeps walking.

Of course you have to know Peter Alway. :D

I've made a lot of clones and nobody has ever taken a ruler to my fins.

The term I've used is "commercially acceptable".

"dimensional inexactness" ??
Is that a precision value ? :D
How far off does a dimension have to be before it is "inexact" ?
I like that sort of terminology....it fits into my hobby philosophy of "good enuff/that'll doo"